获取文本框以仅接受 vb.net 中的字符
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Get a textbox to accept only characters in vb.net
提问by EqEdi
I'm creating a simple application in Vb.net where I need to perform certain validations. So I want a name textbox to accept only characters from a-z and A-Z for example.
我正在 Vb.net 中创建一个简单的应用程序，我需要在其中执行某些验证。所以我想要一个名称文本框只接受来自 az 和 AZ 的字符。
For this I wrote the following code:
为此，我编写了以下代码：
Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) > 65 Or Asc(e.KeyChar) < 90 Or Asc(e.KeyChar) > 96 Or Asc(e.KeyChar) < 122 Then
e.Handled = True
End If
End If
End Sub
But somehow it is not allowing me to enter characters. When I try to enter any character it does nothing.
但不知何故，它不允许我输入字符。当我尝试输入任何字符时，它什么也不做。
What causes this problem and how can I resolve it?
是什么导致了这个问题，我该如何解决？
回答by John Woo
Alternatively, you can do something like this,
或者，你可以做这样的事情，
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) _
Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyz"
If Not allowedChars.Contains(e.KeyChar.ToString.ToLower) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
or if you still want the ASCIIway, try this,
或者如果你仍然想要这ASCII条路，试试这个，
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
If Not ((Asc(e.KeyChar) >= 97 And Asc(e.KeyChar) <= 122) Or (Asc(e.KeyChar) >= 65 And Asc(e.KeyChar) <= 90)) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
both will behave the same.
两者的行为都是一样的。
回答by charles
Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If AscW(e.KeyChar) > 64 And AscW(e.KeyChar) < 91 Or AscW(e.KeyChar) > 96 And AscW(e.KeyChar) < 123 Or AscW(e.KeyChar) = 8 Then
Else
e.KeyChar = Nothing
End If
End Sub
I hope this helps!
我希望这有帮助！
回答by Dog Lover
This is a more abstract approach, but still effective nonetheless. It's straightforward and can just be added to the TextChangedevent. You can use it with multiple textboxes by adding their handles to the sub and using a DirectCast().
这是一种更抽象的方法，但仍然有效。它很简单，可以添加到TextChanged事件中。您可以通过将其句柄添加到 sub 并使用DirectCast().
Dim allowed As String = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
For Each c As Char In TextBox.Text
If allowed.Contains(c) = False Then
TextBox.Text = TextBox.Text.Remove(TextBox.SelectionStart - 1, 1)
TextBox.Select(TextBox.Text.Count, 0)
End If
Next
Summary:If an invalid character is entered, it will immediately be deleted (most of the time the character won't be visible long enough for the user to notice).
总结：如果输入了无效字符，它将立即被删除（大多数情况下，该字符的可见时间不足以让用户注意到）。
回答by Purushottam Kumar
Private Sub txtStudentName_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtStudentName.KeyPress
If Not Char.IsLetter(e.KeyChar) And Not e.KeyChar = Chr(Keys.Delete) And Not e.KeyChar = Chr(Keys.Back) And Not e.KeyChar = Chr(Keys.Space) Then
e.Handled = True
End If
End Sub
